ci: isolate cloud relay tests from unit shards

Run cloud relay integration tests once and exclude them from general shards, while caching the cloud lockfile inputs.

.github/workflows/unit-tests.yml

@@ -40,13 +40,6 @@ jobs:
       - name: Install Electron package binary for tests
         run: node config/scripts/install-electron-package-binary.mjs
 
-      # The real two-cell transport test imports cloud relay source and its contracts.
-      - name: Install relay integration dependencies
-        working-directory: cloud
-        run: |
-          npx --yes pnpm@10.24.0 --filter '@orca-cloud/relay...' install --frozen-lockfile --ignore-scripts
-          npx --yes pnpm@10.24.0 --filter '@orca-cloud/relay^...' build
-
       - name: Test shard
         env:
           ORCA_BALANCE_UNIT_SHARDS: '1'
@@ -71,6 +64,8 @@ jobs:
             --exclude=src/shared/pty-reply-echo-shapes.node-pty.test.ts \
             --exclude=src/shared/startup-shell-portability.live-shell.test.ts \
             --exclude=src/shared/posix-command-path-lookup.test.ts \
+            --exclude=tests/e2e/relay-region-compatibility.unit.test.ts \
+            --exclude=tests/e2e/relay-region-correction.unit.test.ts \
             --exclude=tests/e2e/cross-version-wire/** \
             --shard=${{ matrix.shard }}/${{ matrix.shard_total }}
 
@@ -84,3 +79,38 @@ jobs:
           path: ci-shards/
           retention-days: 14
           if-no-files-found: warn
+
+  relay_integration:
+    name: relay integration node ${{ fromJSON(inputs.node_versions)[0] }}
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - uses: ./.github/actions/install-node-dependencies
+        with:
+          native-runtime: node
+          node-version: ${{ fromJSON(inputs.node_versions)[0] }}
+          cache-electron-package: 'true'
+          cache-dependency-path: |
+            pnpm-lock.yaml
+            cloud/pnpm-lock.yaml
+
+      # These two tests import the cloud relay workspace directly. Keeping them in one job
+      # avoids installing and building the same workspace once per unit-test shard.
+      - name: Install relay integration dependencies
+        working-directory: cloud
+        run: |
+          npx --yes pnpm@10.24.0 --filter '@orca-cloud/relay...' install --frozen-lockfile --ignore-scripts
+          npx --yes pnpm@10.24.0 --filter '@orca-cloud/relay^...' build
+
+      - name: Test relay integration contracts
+        env:
+          ORCA_BACKGROUND_LAUNCH: '1'
+        run: >-
+          pnpm exec vitest run --config config/vitest.config.ts
+          tests/e2e/relay-region-compatibility.unit.test.ts
+          tests/e2e/relay-region-correction.unit.test.ts